With the proliferation of the Internet in recent years, the move to implement various WEB servers and various kinds of services, such as electronic mail, IP telephony, and moving image transfer has been proceeding rapidly. With this trend, the importance of Quality of Service (QoS) control at network node devices that support the Internet has been increasing.
In the case of the services expected to be provided by next-generation networks, etc., the quality of service is guaranteed in principle by providing a sufficient data transmission bandwidth to the network. On the other hand, in the case of the services provided by WEB servers, including services such as IP telephony and moving image transfer, a sufficient data transmission bandwidth is not necessarily guaranteed because such services are provided on the existing Internet.
In the prior art, Tail Drop and Random Early Detection (RED) are proposed as methods for discarding data in the event of packet buffer congestion. An edge node device is also proposed that performs RED by varying the packet discard rate according to the packet residence time. Further, a data flow amount control device is disclosed that calculates the length of time during which a packet to be transmitted from a base station to a mobile station is expected to be held in a buffer at the base station. There is also disclosed a data transmission method that reads from data to be transferred the time at which the data needs to arrive at the destination, and that discards the data packet if it is determined that the data will not arrive at the destination by the requested arrival time.
Related art is disclosed in B. Braden, D. Clark, J. Crowcroft, “Recommendations on Queue Management and Congestion Avoidance in the Internet”, RFC2309, IETF, April 1998, and Japanese Laid-open Patent Publications No. 2005-348166, No. 2008-53851 and No. 9-18510.